I took the plunge yesterday and registered for the Server 2008 Beta Exams, 71-646 and 71-647. Combined with some tinkering of the Betas and RC's of Server 2008 and the free Server 2008 eBook I might have a chance of doing alright. I've got nothing to lose since the exams are free with the voucher codes. I guess we'll find out just how well I do in about 2 weeks.
If you're planning on taking the exams yourself I'd recommend checking the Microsoft Preparation Guides first: